One person creates a ranked lobby, the other person does a ranked quick search. You should match up fairly easy (1 time I found a random). Once you arrive at the character selection screen you can quit and the match will be offical. It will even tell you how many wins you have as soon as the person quits, so you know how far you need to go still. You can boost all 3 online achievements this way(5 straight wins, 10 total wins, 20 total wins).